Seatbelt assemblies are in widespread use in motor vehicles. Present systems have certain common elements including seatbelt webbing which extends across the upper and lower torso of the occupant, and a retractor for allowing extraction and retraction of the webbing so that the belt may adapt to different sizes of occupants and be conveniently out of the way when not being used. Seatbelt assemblies further typically include a buckle which releasably attaches to a latch plate.
As vehicle safety requirements advance, it is desirable for some system designs to detect the presence of a vehicle occupant at least in part through detecting a fastened seatbelt buckle. One manner of detecting the presence of a vehicle occupant is the use of an on/off switch design, which includes an electrical circuit that can be opened/closed in response to insertion of the latch plate into the belt buckle. However, there is a concern if the conductors or connectors of the circuit become damaged or severed the ability to determine a fault in the system is not possible. There are designs that can detect such a fault, but include a large number of additional connecting wires, are high cost, or of large size.
It is desirable in the automotive industry to reduce size, weight, and cost of automotive components, and there is a need for a reliable occupant detection design that can use a two wire circuit in a small package.